Window of opportunity

Building a luxury home may seem counterproductive to the concept of sustainability. The current popularity of the “not so big” house (a term you may have heard from Susan Susanna’s series of books by the same name) and the even smaller subculture of the “tiny house” undoubtedly illustrate a greener way to build, with less material needed and smaller spaces to heat and cool. But these homes are often impractical for a family of more than…one. You can rid yourself of half your possessions, but it’s likely you’ll still want a room of your own, a bit of space to stretch out in, and the luxuries that create a beautiful and comfortable home for family and guests. There are indeed ways to build a spacious luxury home in tune with sustainable design. One of the most effective is to choose windows and doors that incorporate energy-saving materials and technology.

Windows and doors are the major culprit of energy loss in a home, with most U.S. homes losing approximately 20% of their energy through openings. Doors are a little less critical as they typically account for a much smaller percentage of the exterior wall than windows and generally contain less glass, which is the weak link. To illustrate, an Energy Star compliant window with a U-value of .3 has an equivalent R-value of 3.3. Not bad for a window…but it sits in a wall that is R-19 or better. Dave Jenkins, designer of the Energy Saver Plus plans, says, “Installing low-performing windows and doors in one of our cutting-edge designs is just like leaving one open 24-7.”

While windows and doors may be inefficient from a heating and cooling perspective, they provide natural light and reduce the amount of energy required to light the home. The past decade’s advances in window technology have helped to mitigate and balance the drawbacks of window glass by making it more efficient while preserving the benefits of natural light and expansive views.

To accurately place, protect, and select windows, work with an energy modeler who will provide a HERS rating. The Home Energy Rating System (HERS) equates to a miles-per-gallon rating that can be used during the design/build process to compare various strategies and products. According to Scott Rodwin, principal at Rodwin Architecture in Boulder, Colo., “The IECC climate zone chart is also a good place to start planning, as it lists the performance requirements necessary for windows to meet code in different parts of the country. For example, in cloudier cooler climates, you generally want to maximize the SHGC on the south face and decrease your overhangs to increase passive solar gain. In sunny hot locations, you would want to do the reverse. Overall, the total ratio of window to floor area should be below 18%, with the majority of windows on the south. The southern exposure is the easiest side on which to control solar gain by blocking it in the summer and allowing it in the winter.”

Windows can become an asset from a heating perspective. Properly arrayed on the south side of a house, they may contribute to passive solar heating. In fact, the way a home is oriented to the compass points can have an even more significant impact on energy efficiency than the types of windows chosen. Overhangs, insulating blinds, and specific window types can be used in conjunction with the orientation of the home to minimize energy loss. Rodwin Architecture always begins a design by orienting the home to optimize passive solar benefits. That generally means running the main ridge of the roof east to west, and strategically sizing and placing overhangs that protect the south-facing windows from summer sun yet allow the sun’s rays to penetrate in the winter when it is low on the horizon. To frame critical views on the east or west, they simply use deep overhangs and individual picture windows instead of large banks of unprotected glass.

Designers take all of these factors into consideration when specifying windows and they are continually seeking the optimal intersection of price, energy performance, and overall design. There are a wide variety of windows and doors that meet these needs, with several manufacturers standing out in the crowd. Rodwin typically uses metal clad wood windows on high-end projects, as their solid quality and exterior durability can stand up to the strong Colorado sun and freeze/thaw cycle. For metal clad wood windows, he prefers Pella, Hurd, Jeld-Wen, Sierra Pacific, Weather Shield, or Andersen. When the budget allows and for his most energy- efficient homes, which are considered “near net zero” for energy consumption, he specifies fiberglass windows for optimal energy performance and durability. For entry doors, Therma-Tru fiberglass insulated doors beat the competition as a durable, energy-efficient, and cost- effective product.

Jenkins also prefers Andersen windows, and typically specifies the Andersen A-Series and 400 Series for custom clients. Andersen has an extensive variety of options for exterior color, interior wood species, finishes, and hardware, and Jenkins is convinced that their High¬Performance, Low-E4 glass is the best in the business. For the Energy Saver Plus designs, Jenkins specifies Andersen’s new 100 Series. The Fibres composite window frames and sashes are made with 40% pre-consumer reclaimed wood fiber and are more resistant to expansion and contraction. “They’re made to compete with vinyl windows, but are twice as stable. Even the glass in the 100 Series is 12% reclaimed. They are great looking windows and patio doors, with five exterior colors to choose from,” says Jenkins. The 100 Series is even available in hard-to- find dark colors.

One of the best ways to choose a window manufacturer is to match the specific design needs to what the company offers. Rodwin says, “If designing a large bank of windows and doors combining to form a view wall, we will pick a company that provides an integrated line of windows and matching doors so that headers and finishes all match. We also ‘tune’ the glass of all our windows in order to create the best passive solar envelope for the house; some manufacturers are more adept and cost-effective for the varied glazing options that make tuning possible.” Tuning means selecting the best glazing option for each wall’s windows depending on which direction they face. Glazing choices are not cut-and-dry even within a given climate zone. Certain combinations of U-value, emissivity, and SHGC work best on the south side, while others work best on the north, east, and west. When choosing your window supplier, make sure the glazing combinations you require are offered in the style you prefer.

People building luxury homes often desire large expanses of glass such as sliding doors or window walls. These types of doors can be particularly challenging because in an effort to create clean thresholds and easy operation, the gaskets that prevent air infiltration may be sacrificed. Rodwin prefers products such as the Liftslide series from Weiland.

To maximize daylight with minimal sacrifice from a heating and cooling perspective, consider installing sun tubes. Like skylights, sun tubes open to the roof, but the light travels down through a reflective tube in the ceiling and into almost any room in the house. Sun tubes have far less surface area than windows or regular skylights, so there is less heat transfer, no glare, and unlike regular light fixtures, they don’t generate heat of their own.

Despite the advances of the past decade, Rodwin says, “Even the best window is still far less efficient than the worst wall.” Given the rising cost of energy, homeowners should consider how their windows’ efficiency affects the true cost of home ownership. An up-front investment in high-performance windows will result in real savings for years to come, as well as greater comfort and enjoyment of your home.

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